Phase change materials (PCM) are thermal storage materials that are capable of storing large amounts of thermal energy that can be useful in moderating daytime-to-nighttime temperature fluctuations. At present a great deal of interest and markets exist for PCM. Well engineered lightweight structures utilizing PCMs typically reduce cycling of heating and cooling machinery and cause the buildings temperatures to more closely remain in the comfort zone for occupants. PCMs can be hydrated salts, plastic crystals, hydrated salts with glycols or hydrocarbon waxes. Ciba Specialty Chemicals' U.S. Pat. No. 6,716,526 and BASF U.S. Pat. No. 6,200,681 describe manufacturing processes for making microencapsulated hydrocarbon wax phase change particles. The manufacturing process of microencapsulated phase change material (mPCM) produces an aqueous emulsion that contains both solids and liquids. The solids portion, for example 42 to 48 weight percent, are PCM wax particles encased by shell of acrylic or other polymer material. The liquid portion contains from 58 to 52 weight percent water with wax and acrylics residues not bound up to the solids in the production process. In the past, for some applications it has been necessary to remove the encapsulated PCM solids from the acrylics dispersion in the slurry by a costly drying process to effectively incorporate encapsulated PCM into most other products.
An obstacle to the acceptance of organic PCM (e.g., hydrocarbon waxes) in building materials has been that such PCM may be inherently flammable. The PCM itself may be a hydrocarbon, typically a paraffin, that burns very easily. The PCM capsule material, whether of an acrylic polymer or another polymer material (e.g., melamine/formaldehyde resin), or some other material, may also be inherently flammable. There are a number of processes in the prior art for making encapsulated PCM and for the use of PCM in concrete, wallboard, insulation, and other building products.
U.S. Pat. No. 4,747,240, issued May 31, 1988 for Encapsulated PCM Aggregate to Voisinet et al., describes a process in which PCM as an admixture is incorporated directly into a variety of cementitious interior building materials. In that patent, both microencapsulated PCM or “form stabilized”, non-encapsulated PCM, is incorporated directly as an aggregate into a cementitious composition. That patent does not contemplate an aggregate of various sizes, but describes the encapsulated PCM particles themselves as aggregate.
Similarly, U.S. Pat. No. 7,166,355, issued Jan. 23, 2007 for Use of Microcapsules in Gypsum Plaster Board to Jahns et al., discusses a process wherein microencapsulated PCM is incorporated directly into cementitious building material, i.e., wallboard core and plasterboard. This patent states that special steps must be taken to ensure the bonding of all components because of the poor bonding nature of the microencapsulated PCM particles.
WO 2009/059908 discusses compositions containing particles of organic phase change material, particles of fire retarding magnesium hydroxide and/or aluminum hydroxide, and/or magnesia cement. GB 2462740 A discusses compositions with magnesia cement made using magnesium oxide, magnesium chloride and water, and reports moderate first resistance with a low loading of PCM.